Bimetallic circuit breakers



J. ELLENBERGER BIMETALLIC CIRCUIT BREAKERS March 3, 1959 2 sheets-Sheet 1 Filed Sept. 19. 1956 f/VVf/VTR jakob E//En berger J. ELLENBERGER 2,876,311

BIMETALLIC CIRCUIT BREAKERS March 3, 1959 2 Sheets-Sheet 2 Filed Sept. 19. -195:

..//VVENTOR jakob E//enefyer United States Patent O BIMETALLIC CIRCUIT BREAKERS Jakob Ellenberger, Altdorf, near Numberg, Germany Application September 19, 1956, Serial No. 610,823 Claims priority, application Germany July 19, 1956 4 Claims. (Cl. zml-122) The present invention relates to improvements in bimetallic circuit breakers.

It is an object of the present invention to provide a bimetallic circuit breaker which is responsive to both thermal influences and electric overloads for protecting an electric circuit connected thereto.

More specifically, it is ian object of the invention to provide a single circuit breaker which is to respond not only when some apparatus, such as, for example, a mot-or or an electric heating element, should become unduly heated, but also when the current consumption becomes excessive. The bimetallic circuit breaker according to the present invention is therefore provided with a heating coil through which the current ows.

The circuit breakers of this .type as known prior to the present invention had considerable disadvantages. Such circuit breakers should interrupt the current within a period of two minutes if an overload of 100% occurs. However, at a temperature of 100 C. they should be able to withstand the maximum load for a period of four hours. Inorder to accomplish both purposes, it would be necessary to give the bimetallic element a very high initial tension, namely, up to approximately one kilogram. It is, however, practically impossible to build such circuit breakers since such a high' initial tension of the bimetallic element would require an excessive thickness thereof. However, such elements which still. respond properly deform already at a load of 600 grams.

It is fu-rther an object of the invention to provide a bimetallic circuit breaker which avoids the aforementioned disadvantages. .l

This object is attained according to the invention by mounting the contact cooperating with the bimetallic element on a spring so that this contact will abut under the force of such spring against the contact mounted on the -bimetallic element. If the bimetallic element should bend, the contact on the spring will then at first follow the bending motion of the Ibimetallic element with the contacts being in a closed position until the spring comes to a point where its further movement will be prevented by a stop. Not until this time will it be possible that the two contacts between the bemetallic element and the spring can separate. It is thus possible to produce the same results as if the bimetallic element was given a high initial tension, and it will be ensured that the circuit breaker will always respond properly.

A circuit breaker of the type according to the invention has the further advantage that the stop for limiting the movement of the contact spring may be made adjustable, for example, by an adjusting screw so as to regulate the opening movement of the contacts in accordance with different circuit conditions.

According to a preferred embodiment of the invention, the contact spring is made in a bent shape similar to a hairpin since this allows a convenient mounting of the 2 spring within the relatively small housing of the circuit breaker.

According to a further embodiment of the invention, the circuit breaker as described is combined with a starter switch which s preferably likewise a bimetallic switch and provided with contacts at both opposite sides of the bimetallic strip.

By means of such a unit it is thus possible also to control at the same time the auxiliary phase for a motor so that an automatic starting of the motor will be ensured after the cause of an overload or an excessive heating of the motor has been remedied.

The two switches according to the invention are preferably mounted within a single housing so as to save considerably in space and material. The hairpin spring is then placed in a special recess provided in this housing. In order to protect one switch from any possible arcing or heating of the other, it is advisable according to the invention to provide a riblike partition within the housing and between the two switches. The cover of the housing may also be provided with a riblike projection which tits upon the partition in the housing and thus separates the two switch elements entirely from each other and closes the housing.

Furthermore, in order to permit the switch housing also to Ihe mounted on round surfaces, the two opposite side walls thereof are preferably downwardly extended.

The terminal strips of the new bimetallic switch may extend from the housing either above the base and cover portions thereof, in which case the yrecesses for accommodating the strips are preferably provided in the base portion so as to permit the cover portion to be of a simple and inexpensive structure, or they may extend vertically upward and through the cover.

Further objects, features, and advantages of the present invention will be apparent from the following detailed description, particularly when read with reference to the accompanying drawings, in which- Fig. l shows a perspective view of the entire switch unit without its housing;

Fig. 2 shows a top view of Fig. l, but with the switch elements mounted in a housing;

Fig. 3 shows a cross section taken along line III-III of Fig. 2;

Fig. 4 shows a cross section taken along line IV--IV of Fig. 2;

Fig. S shows a cross section taken along line V--V of Fig. 2, but with the cover `attached to the base;

Fig. 6 shows a perspective view of a closed housing with the terminal strips of the switches extending laterally therefrom;

Fig. 7 shows a view similar to Fig. 6, but with the terminal strips extending through the cover of the housing; while Fig. 8 shows a wiring diagram to illustrate one example of the application of the new switch unit.

Referring to the drawings, and particularly to Figs. 1 to 4, a circuit breaker 1 which is responsive to both thermal and electrical overloads, and a switch 2 for controlling the auxiliary phase of a motor for starting the same are both mounted in the base portion 3 of a single housing.

The thermal overload switch 1 consists of a bimetallic st-rip 4 which carries a heating coil 5 which is separated from the bimetallic strip `by a layer of insulating material 6. Current may be supplied to bimetallic strip 4 through a terminal strip 8 projecting from the housing and through a bridge member 7. The current then passes through a contact head 9 to a contact head 10 which is secured to a spring 11 of hairpin-shape which presses contact head 10 resliently against contact head 9 on the Patented Mar. 3,V 1959 vterminal strip 13, which, in turn, is connected t the one end of the spring 11, is adapted to engage to the otherpor free and contact-carrying end of this spring so as to limit the upward movement thereof. As shown particularly in Fig. 3, when the bimetallic strip 4 bends in the direction as shown by arrow 14, contact head will follow the movement of contact head 9 until the free end of hairpin spring 11 engages with screw 12. The two contacts 9 and 10 vwill therefore not open or separate until such engagement of spring 11 with screw 12 takes place, provided the upward bending motion of strip 4 continues.

Bridge 7 combines and connects the thermal overload switch 1 with the starting phase switch 2, and both switches 1 and 2 may be mounted side-by-side within base portion 3 of the housing. Switch 2 likewise consists of a bimetallic strip 15 which carries a heating coil 17 and is separated therefrom by an insulating layer 16. It is likewise connected to terminal strip S. When connected to a circuit, the current then ows through the terminal strip 13 with a contact head 20 thereon. Aside from contact head 19 on the upper side of strip 15, the lower side thereof, at a point directly opposite to contact 19, is preferably also provided with a contact head 21 which engages .with a contact head 22 when the ibimetallic strip 1S bends downwardly so as to protect the heating coil and the birnetallic strip from overheating.

While in the embodiment of the invention, as shown in Figs. l to 5, the terminal strips 8, 13, and 1S extend horizontally, they may `also be bent at an angle and upwardly to extend through suitable slots in the cover 27, as shown in Fig. 7 by numerals 23, 24, and 25.

As shown particularly in Fig. 5, the base portion 3 of the housinv is also provided with a riblike projection 26 which serves as a partition to separate the two switches 1 and 2 from each other. The cover 27 may be provided with a similar riblike projection 28 which will engage rib 26 when cover 27 is placed on base 3, so that the two switch units will then be completely separated and protected from each other.

Fig. 8 shows a wiring diagram to illustrate one particular example of the manner in which the new switch may be used. In this diagram which requires no further explanation, numeral 29 indicates the main phase winding, and numeral 3:0k the auxiliary or starter phase winding of a motor.

While my invention has been described in detail with reference to certain now preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, what I claim as new is:

l. A circuit breaker comprising a base, a bimetallic element mounted at one of its ends on said base and having a contact, a heating coil mounted on said element, a leaf spring of hairpin shape biased in opening direction being secured at the free end of one of its legs to said base `and having a contact close to the free end of the other of its legs, said latter legbeing free to reciprocate towards and away from said one leg by dex-ing about the U-shaped portion of said spring, ,said latter contact being-disposed opposite the contact on said bime- .tallic element and adapted to resiliently engage the same when said element is deflected, an adjustable stop member mounted on said -base in the path of displacement 4of said free end of said leaf spring and adapted to be engaged by the same to limit movement of said leaf spring towards said element, and terminal means on said ibimetallic element and said spring for connecting the same in an electric circuit.

2. A switch unit comprising in combination a circuit breaker responsive to thermal and electric overloads in an electric circ-uit, a starter phase switch, a base, a biinetallic strip forming a heat-responsive organ in said latter switch mounted with one of its ends on said base and having on each side close to its opposite end one contact, a heating coil on said strip, two xed contacts on said base respectively opposite said strip contacts and arranged in such a manner that, in the one switch position, one of said xed contacts is engaged by one lof said contacts on said strip, while the other is disengaged, and in the other switch position, the other Contact is engaged and the one contact is disengaged, a bimetallic element forming a heat-responsive organ in said circuit breaker and being mounted at one of its ends on said base and having a contact, a' heating coil on said element, a leaf spring of hairpin shape biased in opening direction being secured at the free end of one of its legs to said base and having a contact close to the free end of the other of its legs, said latter leg being free to reciprocate towards and away from said Ione leg `by exing about the U-shaped portion of said spring, said latter Contact being opposite the Contact on said bimetallic element and being adapted to resiliently engage the same when said element is detiected, and terminai means on said circuit breaker and said switch to connect said unit in said electric circuit with said two heating coils in series.

3. A switch unit according to claim 2, wherein said circuit breaker and said starter phase switch are housed in a common casing having separate compartments therefor.

4. A swtich unit according to claim 2, wherein said housing has two parts, one being associated with said base and the other forming a cover thereon, and wherein rib-like partitions in said two parts form said separate compartments, said partitions extending from respectively opposite inner walls of said parts to respectively engage one another at an intermediate plane.

References Cited in the le of this patent UNITED STATES PATENTS 1,728,092 whittingham Sept. 10, i929 2,231,463 Dehlendorf Feb. ll, 1941 2,255,672 Mason Sept. 9, 1941 2,329,119 Jacobs Sept. 7, 1943 2,352,713 Hodgkins July 4, 1944 2,499,208 Zimmer -s Feb. 28, 1950 2,673,908 Brumield Mar. 30, 1954 2,754,392 Benedik July l0, 1956 FOREIGN PATENTS 624,038 Great Britain May 26, 19.49

647,659 Great Britain Dec. 20, 1950 1,099,705 France Mar. 23, 1,955

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